The present invention relates to a safety diaphragm for a diaphragm pump, which makes it possible to detect a rupture of the diaphragm during operation or when at a standstill.
Piston diaphragm pumps with hydraulically deflected diaphragms are known, in which the diaphragm consists of at least three individual diaphragm layers lying one on top of the other. The space between the individual diaphragm layers is filled with a buffer fluid. The middle diaphragm layer is provided with slits, which are connected to a display device via a bore. In the event of a diaphragm rupture, in addition to the buffer fluid, pumped medium or hydraulic fluid enters the space between the individual diaphragm layers, and acts upon the display device, signaling the diaphragm rupture. In this case mixing occurs between pumped medium/hydraulic fluid and buffer fluid, which is to be avoided, especially when delivering corrosive fluids.
In other known diaphragm pumps, in particular in the case of mechanically deflected diaphragm pumps, a pressure line leads from a space between different individual diaphragm layers from the pump housing out to a display device. These pressure lines, in particular outside the pump housing, are very susceptible to being bent or crushed, so that with time they start to leak. In the case of these known diaphragm pumps, it is not a diaphragm itself that is monitored with respect to a diaphragm rupture, but the space between different individual diaphragms, which although connected with one another, are otherwise separate from one another and do not represent an hermetically sealed unit.
In the case of diaphragm pumps, a distinction is made between mechanically deflected and hydraulically deflected diaphragm delivery units. To deliver a fluid by means of a diaphragm pump, a piston displacement based on the stroke movement of an operational region of the diaphragm is passed on to the fluid to be delivered. In the case of mechanically deflected diaphragms, the operational region of the diaphragm is deflected by means of an actuating rod perpendicular to the diaphragm surface. Due to the deflection of the diaphragm by means of the actuating rod, alternating compression and suction movements are carried out (compression stroke and suction stroke). In the case of a hydraulically deflected diaphragm, compression and suction strokes are carried out by a hydraulic positive pressure and negative pressure of a hydraulic fluid on the operational region of the diaphragm. The integrated actuating rod supports the suction stroke by means of a return spring.
The objective of the present invention is now to provide a safety diaphragm for diaphragm pumps, which allows safe detection of rupture sites in the diaphragm, functions without a buffer between different diaphragm layers, is simple in construction, requires low maintenance expenditure, prevents mixing of pumped medium/hydraulic fluid, detects a diaphragm rupture before pumped medium/hydraulic fluid can penetrate out through the diaphragm, and does not in any case have to be replaced immediately when a rupture occurs in the diaphragm, but optionally allows emergency operation until the next diaphragm change.